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Roof Structure


The roof structure, as shown in Figure 1, must provide a solid and stable base for the roofing materials. It consists of the structural members, including rafters, trusses and the roof decking.

A variety of structural problems can affect the performance and the longevity of the roofing materials. Movement of the decking, sagging of the decking, movement around openings, movement at connections and expansion or swelling of the decking or sheathing can all affect the roofing materials. Proper attention to details and design can usually resolve these problems.

The performance of the roofing materials can also affect the roof structure. Excessive moisture in the roof decking to deteriorate. This moisture can come from leaks in the roofing materials, from ice damming or from the interior of the house.

Better building techniques, such as more insulation and tighter air barriers, can significantly improve the energy efficiency of the house and reduce the occurrence of such problems as moisture in the attic.

Area Primary Consideration Problem Cause

Roof Structure

Structural Deterioration And Damage

Sagging Roof Sheathing

Inadequate support for the roof sheathing

Sheathing materials too thin to support concrete or clay tile roofing

Sagging roof support structure around openings

Inadequate framing around openings in roof trusses and rafters.

Roof structure sags around truss connections

Inadequate supports and poor fastening of connections,

Sheathing panels rise up at joints, causing ridging.

Roof panels installed too tightly

Water Leakage

Rotting of structural members and sheathing materials

Water leakage due to ice damming.

Excessive moisture in the attic space.

Water leakage around flashings

Additional information on roofs and roofing